Applications of microfluidics for molecular diagnostics

Abstract

Diagnostic assays implemented in microfluidic devices have developed rapidly over the past decade and are expected to become commonplace in the next few years. Hundreds of microfluidics-based approaches towards clinical diagnostics and pathogen detection have been reported with a general theme of rapid and customizable assays that are potentially cost-effective. This chapter reviews microfluidics in molecular diagnostics based on application areas with a concise review of microfluidics in general. Basic principles of microfabrication are briefly reviewed and the transition to polymer fabricated devices is discussed. Most current microfluidic diagnostic devices are designed to target a single disease, such as a given cancer or a variety of pathogens, and there will likely be a large market for these focused devices; however, the future of molecular diagnostics lies in highly multiplexed microfluidic devices that can screen for potentially hundreds of diseases simultaneously.

Fig. 1.

A schematic diagram of a conceptual lab-on-a-chip device designed to perform a variety of unit operations and unit processing steps including: sample preparation (e.g., fluid handling, derivatization, lysis of cells, concentration, extraction, and amplification), sample separation (e.g., electrophoresis, liquid chromatography, molecular exclusion, field-flow fractionation), and detection (e.g., fluorescence, UV/Vis absorption, amperometric, conductivity, Raman, electrochemical).

Fig. 2.

(a) Prototype of an automated nucleotide extraction platform. The microfluidic system consists of five different components: (i) a disposable microfluidic cartridge containing a glass fiber filter (inset figure); (ii) a PDMS-microfluidic chip for flow control; (iii) microfluidic chambers for mixing, metering, pumping, and reactions; (iv) a pneumatic micropump to deliver the eluted sample to downstream assays; and (v) a vacuum pump to control the on-chip valves. The extraction chip also has provision for thermal lysis and reverse transcription (not shown). (b) Prototype of a test socket for characterization of a carbon nanotube-based electrochemical nanosensor array. The test socket provides both fluidic and electrical interface to the nanosensor chip (inset figure) that detects nucleotide hybridization. (c) Prototype of a shuttle PCR chip with three temperature zones and which is fabricated using polycarbonate lamination. The heaters and thermocouples are shown with a manifold for on-chip fluidic control. The fluidic interface for the extraction system is designed so that it can be readily connected to the downstream assays such as hybridization and PCR.